Common Boiler Faults

Modern boilers are very reliable. However, they are not indestructible and things do go wrong. Consequently, most common boiler faults are during the colder months of the year, which just adds to the misery and inconvenience of boiler repairs.

The boiler industry will see a big spike in boiler repair services in winter months when most boilers are switched back on after being off over the warmer summer months. Evidently, it is whenever the weather hits freezing temperatures and boilers are used to their maximum performance for long periods of time.

Is your boiler not working?

It’s not always possible to determine exactly what is causing the boiler problem without physically examining the boiler. Nevertheless, knowing what the symptoms are would help identify possible causes.

Furthermore, if you have a modern boiler then it’s likely that you’ll see an error message or error code on the boiler’s display. Make a note of this because it will help a boiler repair engineer with the diagnosis.

The most common boiler faults cause the following problems:

  • No hot water or heating
  • Pressure issues
  • Boiler switching off
  • Strange or loud noises
  • Leaky boilers
  • Pilot lights gone out
  • Freezing
  • Faulty thermostat
  • Radiators not getting hot
Gas engineer repairing a common boiler fault

What may be causing these common boiler faults?

Is your boiler not working? Here are some brief explanations of what could be causing the boiler to breakdown.

No heat or hot water

Having no heat or hot water could be caused by a number of reasons such as:  low pressure, airlocks, faulty thermostat, valves, a broken diaphragm or another component.

Pressure issues

We recommend you check the pressure first as a boiler may switch off if the pressure becomes too low (below 1bar). To top up the pressure the valves can be opened either by tap handles, or by using a flat headed screwdriver. Open both valves to allow the cold water into the system (you should be able to hear it). Keep an eye on the pressure gauge until it reaches 1.5bar, then close both valves, one after the other.

Noisy Boiler

Boilers that are making loud noises could have a build up of limescale, especially if the boiler is exposed to hard water. Limescale causes a boiler to work harder as sludge builds up in the heat exchanger, the water then overheats causing it to boil or steam, known as the kettling effect. A product which helps to prevent the build up of limescale is a Magnaclean. If the noise coming from the boiler is a banging noise then this is most likely to be an issue with the pump.


A leak from the boiler can be another issue and the source of the leak will help determine the cause of the breakdown. The most common cause of a leak are faulty components such as the pressure valve, pump seal, pipes or the tank.

Pilot light

When the pilot light goes out, causes could be a draught, broken thermocouple or possibly a deposit build up. It’s worth checking the issue isn’t with the main gas supply – test another gas appliance to see if it works.

Pipe freezing

We mentioned that most boiler repairs happen in the colder months when most people are using their boilers more frequently. A fault can arise with a condensing boiler if the condensate pipe freezes. The condensate pipe runs from the boiler to outside the house so inevitably is more exposed to freezing conditions.

If you have identified the pipe then you can take precautionary measures to ensure it doesn’t freeze, however it’s advisable to seek professional advice before doing anything yourself.

We also recommend that if you are considering having a condense boiler installed, then the installation is undertaken by an experienced company or gas safe engineer who factor these things in before installing.

Thermostat controls

The thermostat can sometimes be the cause too, but not because it is faulty but merely because it has been incorrectly set up.

We always try to diagnose over the phone before sending out an engineer, as in many cases the thermostat hasn’t been set up correctly or simply needs resetting. Doing some checks first may save you having to pay unnecessary repair bills.


If you discover that your radiators are not getting hot or parts of the radiators are not heating up, it could be caused by a build up of sludge or air. Try bleeding and/or balancing the radiators and then see if that has fixed the problem.

If your central heating system is quite old then it may require a power flush, or even a new boiler system. We recommend a MagnaClean or Power Flush to help prevent radiators or a boiler not working.

Boiler repair or replacement?

Is your boiler not working and the warranty has run out? Then, it maybe a good time to replace the boiler with a new modem energy efficient one. Maybe the boiler has broken down due to a faulty or worn part. Subsequently, it is possible this may lead to a further faults within the boiler at a later date.

Unsurprisingly, the boiler may have several intermittent issues which cannot be discovered until a part is replaced. Our engineers are trained and experienced to provide honest advice on the best course of action. A new boiler may be better and more cost effective than trying to fix a problematic old inefficient boiler.

If the boiler is over 10 years old then replacing it could also reduce your energy bills. Check our boiler installation services for more information.

Check if you have a boiler warranty

It is worth checking to see if your boiler is under any warranty, as this could save you on the boiler repair costs. A boiler warranty can be anything from 1 year up to 10 years. If you are unsure then you can call the manufacturer directly and they will be able to advise. If your boiler isn’t under warranty then you will need a boiler repair engineer.

Preventing boiler problems

Boiler manufacturers and the Gas Safety authority highly recommended that you have an annual boiler service for safety reasons and to help prevent nasty boiler repair bills. If you still have a boiler warranty, then make sure you check the small print, as it may be a requirement to have an annual service to validate the warranty.

It is also recommended that a boiler isn’t switched off for long periods of time (weeks/months). Having a smart thermostat will help provide the ultimate control over the heating and will also allow users to control the boiler remotely.

Is my boiler safe?

When did you last have it serviced and how old is it?

Boilers are generally very safe and have built in safety features that will switch off the boiler should it detect malfunctions. However, if you suspect something maybe wrong or feel unsafe, then you can turn the boiler off manually and should contact us.

We have written an article on gas safety, which identifies the dangers of poorly installed and maintained gas appliances.

boiler not working

FAQs about Common Boiler Faults

Can you repair a gas boiler yourself?

No, you must never attempt to do anything that involves disturbing the gas carrying components unless you are a registered gas safe engineer.

Although, the definition of gas ‘work’ is quite wide ranging. You can perform tasks set out in the user instructions. Specifically, parts which are external to the boiler such as a thermostat control or topping up the pressure. However, changing or touching parts within the combustion chamber is a no!

Click here to see a fact sheet 

Attempting to fix the boiler yourself is dangerous and could lead to more serious problems such as carbon monoxide poisoning or even an explosion. Boiler not working? Leave it to the professionals.

Beware of illegal gas fitters

It is shocking that recent studies from Gas Safe have raised concerns over the amount of illegal fitters. Moreover, the amount of home owners that didn’t even check for a local Gas Safe engineer was shockingly high. Know who is entering your home.

Gas Safe recently surveyed 2,000 home owners and of those who have had gas work carried out in 2018.

  • 1 in 4 didn’t even think about checking that the engineer was registered and legal.
  • 1 in 6 even went on to admit that they would knowingly employ an illegal gas fitter if they came recommended.
  • 9 in 10 illegal gas jobs are not completed to the required standard.
  • 1 in 5 jobs were so dangerous their investigations officers had to switch the appliance off.

Gas Safe are urging consumers to be more diligent when it comes to who they are letting in.

How to check the Gas Safe register?

Click this link and you can search – Furthermore, all professionals will carry a registration card. Make sure they produce this before doing any work and don’t be afraid to ask. It is your safety at risk if you use an illegal untrained gas engineer.

Safety should always come first.

Is your boiler not working?

Is your boiler not working or if you suspect something is wrong, then call our friendly customer care team on 01628 533 550 Alternatively, you could book an appointment online.

If possible have the follow information to hand, although this is not essential:

  • Boiler make and model
  • Error code if on the display
  • Description of what the issue is with the boiler

Also, as advised earlier, if the boiler is relatively new then check whether it is covered by a warranty!

Common boiler faults December 19, 2017